Snap-action switch assembly

ABSTRACT

A snap-action switch assembly is disclosed. The switch comprises an arm projecting from a first support and having a first end portion thereof supported by the first support, a spring interconnecting a second support and the arm to exert a compressive force on the arm, a spring adjuster supported on a substantially central portion of the spring and selectably presettable to vary the magnitude of the compressive force, and an electrical contact mounted on the end portion of the arm opposite the first end portion and actuatable by angular displacement of the arm. Preferably, the spring adjuster is arranged symmetrically in the middle of the spring, since the effectiveness of the setting is then at its greatest. The spring adjuster directly varies the characteristic of the spring and is attached to the spring itself, so that a very compact form of construction results.

*umttasetes' mt:

Schwarm.

I i i 1. 51 Nov. 12, 1974 [54] SNAP-ACTION SWITCH ASSEMBLY [75] inventor: Hans Schwarm, Katzwang,

Nurnber'g, Germany [73] Assignee: Eberle Werke KG, Nurnberg,

Germany 22 Filed:. Nov.'16, 1973 2 1 AppL/No; 416,474

[30] 7 "Foreign Application Priority Data I .Dec. l4, 1972 Germany 2261039 [52] us. Cl... 337/67, 200/67 13, 200/67 DB,

[51] Int. Cl. H0lh 13/36 [58] Field of Search 200/67 R, 67D, 67 DA,

200/67DB, 83 P; 337/52, 53, 67, 89, 132;

[56] v References Cited UNITED STATES PATENTS 1,869,610- 8/1932 Neureuther...

v 9/1952 Miller 3,733,571 5/l973 Budlane et a Primary Examine rDavid Smith, Jr. Attorney, Agem,or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A snap-action switch assembly is disclosed. The switch comprises an arm projecting from a first support and having a first end portion thereof supported by the first support, a spring interconnecting a second support andth arm to exert acompressive force on the arm, a spring adjuster supported on asubstantially central portion of the spring and selectably presettable 'to vary the magnitude of the compressive force, and

an electrical contact mounted on the end portion of the arm opposite the first end portion and actuatable by angular displacement of the arm. Preferably, the

spring adjuster is arranged symmetrically in the middle of the spring, since the effectiveness of the setting is then at its greatest. The spring adjuster directly varies the characteristic of the spring and is attached to the spring itself, so that a very compact form of construction results.

8 Claims, 4 Drawing Figures SNAP-ACTION SWITCH ASSEMBLY BACKGROUND OF THE INVENTION The present invention relates to a snap-action switch assembly of the kind comprising an arm having one end supported and the respective other end angularly displaceable between, for example, two alternative positions.

Snap-action switch assemblies are provided with electrical contact means which are actuated in response to the displacement of the free end of the arm. Such snap-action switches may be employed, for example, either in the construction of micro switch devices or in the construction of temperature regulating devices. In the latter application, the arm of the switch normally includes a bimetal element which is responsive to changes of temperature to initiate the opening or closing of the contact means. However, particularly in its application to microswitches, the arm may be either a rigid or a resilient elongate member which is displaced by mechanical means in order to initiate the I switching action.

A temperature regulating device is dscribed in Swiss Pat. Specification No. 251,432. The arm of the snapaction switch disclosed in the aforementioned Swiss Patent Specification is a bimetal leaf spring, on the free end of which acts a U-shaped spreading spring. The distance between the limbs of this U-shaped spring may be adjusted by rotating a regulator screw mounted in a threaded bore in th housing of the device and acting upon only one limb of the U-shaped spring. Particular disadvantages of this known device are that the pressure exerted by the spring on the arm is not settable with sufficient accuracy and the setting range is unduly restricted.

SUMMARY OF THE INVENTION According to the present invention there is provided a snap-action switch assembly comprising a first support member, an elongated arm projecting from the first support member and having a first end portion thereof supported by the first support member, a second support member, an elongated spring member interconnecting the second support member and the arm to exert a compressive force on the arm, spring adjuster means supported on a substantially central portion of the elongate spring member and selectably presettable to vary the magnitude of the compressive force, and electrical contact means mounted next adjacent a portion of the arm spaced from the first end portion and actuatable by angular displacement of the end portion of the arm opposite the first end portion.

Preferably, the spring adjuster means is arranged symmetrically in the middle of the elongate spring member, since the effectiveness of the setting is then at its greatest. The spring adjuster means directly varies the characteristics of the elongate spring. The spring adjuster means is attached to the spring itself and, thereby, a very compact form of construction results.

Advantageously, the spring adjuster means comprises a tensioning screw passing through the elongate spring member and provided with a clamping nut. The stiffness of the elongate spring member, and hence the magnitude of the compressive force exerted on the arm, may be increased by tightening the screw of clamp the spring more firmly between the head of the screw and the cooperating clamping nut. The resilient bias exerted by the spring on the arm can also be varied by exchanging one tensioning screw for another one with a different sized head.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be more particularly described with reference to the accompanying drawings, in which:

FIG. 1 shows in side elevation a snap-action switch provided with a resiliently biassed contact carrying arm having one end provided with a knife edge and resiliently urged into contact with walls of recess in a sup porting wall;

FIG. 2 shows another view of the switch shown in FIG. 1, with the contact carrying arm in a different switching position and having one end firmly clamped to a supporting wall;

FIG. 3 shows a modified embodiment of the invention; and

FIG 4 shows a detail of the embodiment illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A snap-action switch embodying the invention may be employed in the construction of a micro-switch or, particularly when the lever arm 1 is a bimetal leaf spring, in the construction of a temperature dependent switch. An end portion 2 of a lever arm 1 is supported in a recess in the wall 4 of a housing. The extremity of the lever arm 1 contacting the housing is provided with a knife edge 3. At the other end, the lever arm 1 carries a switch contact 5, which, when in the contact position shown in FIG. 1, cooperates with a locally fixed counter-contact 6. The counter-contact 6 is rigidly supported by any suitable means which, in the interest of clarity have not been shown in the drawing. FIG. 2 shows the switch with its contacts 5 and 6 spaced apart. In this condition, the movable contact 5 rests against a stop 7. As indicated in FIG. 2, the end portion 2 of the arm 1 is firmly clamped to a rigid wall. The means by which the end portion 2 of the arm 1 is firmly clamped to the wall have not been shown in FIG. 2, but may comprise a socket in the wall into which the end portion of the arm is firmly wedged.

The free end of the arm 1 is provided with a knife edge bearing 8, which receives one end of a leaf spring 9. The opposite end of the leaf spring 9 is supported in a recess 10 in a support 12. In the illustrated embodiments, the snap-action switch is actuated mechanically by displacement of a pin 11 to vary the laterally directed pressure exerted by the pin 11 on the arm 1. Such a snap-action switch may also be mehanically actuated by displacement of the support 12 in the direction indicated by the double-headed arrow in FIG. 2. However, in other embodiments, the arm 1 comprises a bimetal leaf spring element and, in these circumstances, the switch is actuated when the tension in such a bimetal element is increased as a result of changes in temperature to such an extent that the bias force exerted thereon by the spring 9 is exceeded. In this case, the temperature responsive characteristic of the arm I (which is then constructed as a bimetal leaf spring) can be adjusted by varying the position of a threaded pin 11 to change the contact pressure between the pin and the bimetal element.

In the embodiment illustrated in FIGS. 1, 2 and 4, a tensioning screw 13 which passes through a corresponding bore in the spring 9 and is screwed up relative to a clamping nut provides means for varying the bias exerted by the spring 9 on the arm 1. A clamping plate 14, which is restrained against rotation by the engagement of bent-over lugs 15 in respective recesses 16 of the spring 9, serves as the lock nut. As the screw 13 is tightened, the resilient bias exerted by the spring 9 on the arm 1 is increased.

In the embodiment illustrated in FIG 3, the spring 9 is provided with a rectangularly shaped portion 18. Screwed into a threaded bore in one limb 19 of this portion 18 is a tensioning screw 20, and an end portion 21 of the screw is pressed against a further limb 22 of the portion 18. The resilient bias exerted by the spring 9 on the arm 1 in FIG. 3 may be adjusted by rotating the screw 20 to vary the pressure which it exerts on the two limbs 19 and 22. As this pressure is increased, the limbs are forced further apart and, consequently, the resilient bias exerted by the spring 9 is increased.

In the embodiments which have been described with reference to the accompanying drawings, the electrical contact means comprise one contact element mounted on an end portion of the arm and another mounted next adjacent the first. However, other forms of construction of the contact means may be adopted. For example, the contact means may comprise two spring contact elements, neither of which is supported on the arm, but which are so mounted next adjacent the de flectable end portion of the arm that when the arm is deflected such spring contact elements are urged together to contact one another in response to the movement transmitted to one of the contact elements by the displacement of the arm.

I claim:

1. A snap-action switch assembly comprising, in combination:

a first support member;

an elongate arm projecting from said first support member and having a first end portion thereof supported by said first support member;

a second support member; 1

an elongate spring member interconnecting said second support member and said arm to exert a com pressive force on said arm;

spring adjuster means supported on a substantially central portion of said elongate spring member and being selectably presettable to vary the magnitude of said compressive force; and

electrical contact means mounted next adjacent a portion of said arm spaced from said first end portion and actuatable by angular displacement of the end portion of said arm opposite said first end portion.

2. An assembly as defined in claim 1, wherein said adjuster means comprises a headed member having a threaded shank passing through said elongate spring member to engage a cooperating thread on a clamping member, said clamping member cooperating with the head of said headed member to clamp a substantially central portion of said elongate spring member therebetween.

3. An assembly as defined in claim 2, wherein said clamping member comprises means to restrain said clamping member against rotation relative to said elongate spring member.

4. An assembly as defined in claim 3, wherein said restraining means comprises, at least, one lug projecting from said clamping member to enter a respective recess in said spring member.

5. An assembly as defined in claim 1, wherein said elongate spring member comprises a central portion having two mutually facing limbs, one of said limbs having a threaded passage, and wherein said adjuster means comprises a threaded .member extending through said threaded passage to contact the respective other one of said limbs.

6 An assembly as defined in claim 5, wherein said mutually facing limbs are substantially parallel to each other.

7. An assembly as defined in claim I, wherein said electrical contact means comprises at least one contact element supported on said arm.

8. An assembly as defined in claim 1, wherein said arm comprises a bimetal element. 

1. A snap-action switch assembly comprising, in combination: a first support member; an elongate arm projecting from said first support member and having a first end portion thereof supported by said first support member; a second support member; an elongate spring member interconnecting said second support member and said arm to exert a compressive force on said arm; spring adjuster means supported on a substantially central portion of said elongate spring member and being selectably presettable to vary the magnitude of said compressive force; and electrical contact means mounted next adjacent a portion of said arm spaced from said first end portion and actuatable by angular displacement of the end portion of said arm opposite said first end portion.
 2. An assembly as defined in claim 1, wherein said adjuster means comprises a headed member having a threaded shank passing through said elongate spring member to engage a cooperating thread on a clamping member, said clamping member cooperating with the head of said headed member to clamp a substantially central portion of said elongate spring member therebetween.
 3. An assembly as defined in claim 2, wherein said clamping member comprises means to restrain said clamping member against rotation relative to said elongate spring member.
 4. An assembly as defined in claim 3, wherein said restraining means comprises, at least, one lug projecting from said clamping member to enter a respective recess in said spring member.
 5. An assembly as defined in claim 1, wherein said elongate spring member comprises a central portion having two mutually facing limbs, one of said limbs having a threaded passage, and wherein said adjuster means comprises a threaded member extending through said threaded passage to contact the respective other one of said limbs.
 6. An assembly as defined in claim 5, wherein said mutually facing limbs are substantially parallel to each other.
 7. An assembly as defined in claim 1, wherein said electrical contact means comprises at least one contact element suppOrted on said arm.
 8. An assembly as defined in claim 1, wherein said arm comprises a bimetal element. 